A variety of coloring and whitening agents are known and useful in treating fabrics. For example, bluing agents are used to mask the undesirable yellow color of fabrics following laundering. Typical coloring agents include dyes and pigments, such as ultramarine blue, and optical brighteners.
Many coloring agents are substantially insoluble in aqueous solutions, and when added during a laundering process are in particulate form. During laundering, if the particles of coloring agents are sufficiently small and dispersed in the laundry solution, then the particles become deposited on the fabrics and mask the yellowed color of the fabrics by partially compensating for the absorption of short wavelength blue. Some particulate coloring agents lose effectiveness in oxidizing environments, such as hypochlorite bleach solutions, although addition of such agents in conjunction with laundering additives is a convenient means of treating fabrics.
U.S. Pat. No. 4,271,030, issued June 2, 1981, inventors Brierley et al., discloses a liquid hypochlorite bleach having a particulate pigment, such as ultramarine blue, which is said to be stably suspended in the composition by means of a flocculant filling at least 50% of the volume of the composition.
U.S. Pat. No. 3,666,680, issued May 30, 1972, inventor Briggs, discloses an encapsulating material for particles said to be useful in protecting optical brightening agents in aqueous bleach. The encapsulating material disclosed is a styrene polymer, and encapsulation is by means of a two-stage polymerization method.
Prior methods for making encapsulated brightening agents have been multi-step, or difficult to control, and known compositions with brightening agents in aqueous solutions have posed sedimentation, coagulation or stability problems.